1. Field of Invention
The present invention relates to a control device and in particular to a motor control device.
2. Related Art
In the field of motor controlling, a Hall sensor can be used in sensing the positions of rotating magnetic poles (magnets in the rotor) in a motor. Therefore, the rotation of the motor can be monitored by appropriately positioning the Hall sensors in the motor.
As shown in FIG. 1 and FIG. 2. A Hall sensor 11 is disposed at a position P1 to sense variations in the magnetic poles (magnets in the rotor) during the rotation of the motor 12. A controller 13 is connected to the hall sensor 11 for adjusting the driving current 121 of the motor 12 according to the sensing result of the Hall sensor 11.
However, if the Hall device 11 is still disposed at the position P1, it is easy to generate a surge during the driving current 121 being close to its reverse point when the rotation speed of the motor 12 increases (FIG. 2). Moreover, the phase of the driving current 121 will fall behind the phase of the driving voltage of the motor 12. Therefore, the motor 12 is likely to produce noises and operates with a worse efficiency.
To improve the above-mentioned situation, the Hall sensor 11 is disposed at a position P2. As a result, the phase difference between the driving current 121 and the driving voltage can be reduced, and the surge occurring when the driving current 121 is close to its reverse point during high-speed operations of the motor 12 can be improved. Therefore, the motor 12 produces fewer noises and operates more efficiently. Nevertheless, the motor 12 has lower efficiency and larger noises during low-speed operations. Consequently, the best position of the Hall sensor 11 varies with the rotation speed of motor 12. Whether it is disposed at the appropriate position affects the control efficiency of the controller 13 over the motor 12.